A polycarbonate polyol is a useful compound as a starting material for preparing a polyurethane resin which is used for preparing a hard foam, a soft foam, a paint, an adhesive, artificial leather, ink binder etc., by the reaction with an isocyanate compound.
Also, it has been known that a coating film obtained by coating an aqueous polyurethane resin dispersion containing a polycarbonate polyol as a starting material is excellent in light resistance, heat resistance, hydrolysis resistance and oil resistance (see Patent Literature 1). However, when a material comprising an aliphatic polyol is used as a polycarbonate polyol, there are problems that hardness of the coating film obtained from an aqueous polyurethane resin dispersion is insufficient, for example, in the field of a paint or in the field of a coating agent for an outer board for an airplane, automobile, etc., and for an outer wall surface and floor material, etc., of a house.
Thus, to improve the hardness of the coating film, it has generally been proposed to use an aqueous polyurethane resin dispersion which employs a polyol having an alicyclic structure. However, when the polyol having an alicyclic structure is used as a starting material, dispersibility into an aqueous medium becomes worse, and there are problems in handling property and stability of the aqueous polyurethane resin dispersion.
There is disclosed an example of an aqueous polyurethane resin dispersion using a polyol actually having an alicyclic structure (see Patent Literature 2), but an effect on hardness of the coating film obtained by coating the aqueous polyurethane resin dispersion is unknown, and dispersibility thereof in an aqueous medium is not satisfied.